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Transcript of FIELD EFFECT TRANSISTOR - India’s Premier Educational ... · PDF fileFET ( Field Effect...

  • FIELD

    EFFECT

    TRANSISTOR

    by A.AsunthaA.P(O.G)

    Department of EIESRM University

  • FET(FieldEffectTransistor)

    Few important advantages of FET over conventional Transistors

    1.Unipolar device i. e. operation depends on only one type of charge carriers (h or e)

    2. Voltage controlled Device (gate voltage controls drain current)

    3. Very high input impedance (109-1012 )

    4. Source and drain are interchangeable in most Low-frequency applications

    5. Low Voltage Low Current Operation is possible (Low-power consumption)

  • FET(FieldEffectTransistor)

    6. Less Noisy as Compared to BJT

    7. No minority carrier storage (Turn off is faster)

    8. Self limiting device

    9. Very small in size, occupies very small space in Ics

    10.Low voltage low current operation is possible in MOSFETS

    11. Zero temperature drift of out put is possible

  • TypesofFieldEffectTransistors(TheClassification)

    MOSFET(IGFET)

    n-Channel EMOSFET

    p-Channel EMOSFET

    Enhancement MOSFET

    Depletion MOSFET

    n-Channel DMOSFET

    p-Channel DMOSFET

    FETJFET n-Channel JFET

    p-Channel JFET

  • TheJunctionFieldEffectTransistor(JFET)

  • Gate

    Drain

    Source

    SYMBOLS

    n-channel JFET

    Gate

    Drain

    Source

    n-channel JFETOffset-gate symbol

    Gate

    Drain

    Source

    p-channel JFET

  • BiasingtheJFET

  • OperationofJFETatVariousGateBiasPotentials

  • P P+

    -

    +

    -+

    -

    N

    N

    OperationofaJFET

    Gate

    Drain

    Source

  • Nonsaturation(Ohmic)Region:

    Thedraincurrentisgivenby

    =

    2

    2 2

    2DS

    DSPGSP

    DSSDS

    VVVV

    V

    II

    =

    2

    2 PGSP

    DSSDS

    VVV

    II

    2

    1 and

    =

    P

    GSDSSDS V

    VII

    Where,IDSS istheshortcircuitdraincurrent,VP isthepinchoffvoltage

    OutputorDrain(VDID)CharacteristicsofnJFET

    Saturation(orPinchoff) Region: